It is conventional practice in dry casting of concrete pipe products to dispose a mold on the base of a concrete pipe machine that is provided with a vertically movable crosshead having a vertically driven shaft on the lower end of which a packer head is attached. The packer head typically includes a troweling cylinder which is rotated in one direction by the driven shaft, and a plurality of distributing rollers which are frictionally driven by engagement with the concrete in a direction opposite to that of the driven shaft on the troweling cylinder. With the packer head moved to its lowermost position so the top is at or below the level of a lower pallet, cement or concrete is fed to the interior of the mold. Then, as the crosshead is raised causing the packer head to be raised, the friction driven rollers pack the cement or concrete against the inner surface of the mold and the troweling cylinder is counter-rotated to finish the inner surface thereby forming the pipe. When the packer head reaches an upper pallet, the pipe is completed. The packer head is then withdrawn from the finished pipe and the form thus provided with a molded pipe is replaced by an empty form and the pipe molding process repeated. The self-supporting formed pipe is then demolded and stored to reach a sufficient set strength after an initial curing to enable handling of the pipe and removal from the pallet.
One of the problems in the manufacture of tubular concrete pipe by the packer head method is that foreign material or particles in the incoming concrete flow can become lodged between the troweling cylinder and one or more of the distributing rollers, thereby causing the rollers to stick or jam. When jamming of this nature occurs and one or more of the rollers does not rotate, the compaction of the concrete becomes uneven and the quality of the pipe formation suffers accordingly. It is therefore desirable to provide a packer head type device which prevents sticking or jamming of the rollers without adding complex structure and undue costs. It is also desirable to improve the quality of compaction without resorting to an externally driven source for driving the distributing rollers.
It is a broad object of the present invention to provide a concrete pipe manufacturing machine having a linkage arrangement for collectively driving the rollers so as to not only compact but to extrude concrete in a highly efficient manner.
It is a further object of the present invention to provide a concrete pipe manufacturing machine having a transmission arrangement coupling each of the rollers together to define a synchronous friction drive for equalizing the frictional forces applied to the rollers.
Yet a further object of the present invention is to provide a concrete pipe manufacturing machine employing chain driven roller assemblies for driving the rollers at the same speed.
Still a further object of the present invention is to provide a method of manufacturing concrete pipe using a stepped roller configuration and an arrangement coordinating the motion of the friction driven rollers.
Still another object of the present invention is to replace the known packer head device with an extruder head assembly which improves the quality of concrete pipe formation.
In one aspect of the invention, a concrete pipe manufacturing machine movable in a mold for receiving a concrete mixture to form a tubular concrete wall includes a troweling cylinder assembly having a head plate. A vertically movable and rotatable drive shaft is fixed to the head plate for moving the troweling cylinder assembly in a vertical direction and in one rotational direction. A series of roller assemblies are rotatably mounted on the head plate and adapted to be rotated by frictional contact with the concrete wall in a direction counter to the one rotational direction of the drive shaft. A linkage arrangement interconnects and collectively drives the roller assemblies together for preventing jamming of the roller assemblies due to material in the concrete mixture. Each of the roller assemblies includes a stepped roller including a first segment having a first diameter and a second segment having a diameter smaller than the first diameter. The roller has a support shaft rotatably supported in a bearing unit fixed to the head plate, the bearing unit spacing the roller above the head plate. The troweling cylinder has a cylindrical sidewall in vertical alignment with an outer edge of the roller first segment. The roller second segment is provided with at least one concrete-slinging vane. The roller assemblies are concentrically located on the head plate and spaced around the periphery thereof. The linkage arrangement includes a drive sprocket located on each of the roller assemblies, and a transmission band engaging each drive sprocket. The linkage arrangement further includes a set of idler sprockets interengaged by the transmission band, each of the idler sprockets lying between adjacent drive sprockets. In the preferred embodiment, the transmission band is a chain.
Another aspect of the invention relates to an improvement in a concrete pipe manufacturing machine having an extruder head assembly axially movable and rotatable about the longitudinal axis of a mold to which a concrete mixture is delivered, the extruder head assembly including a series of friction driven rollers engageable with the concrete mixture. The improvement relates to a transmission arrangement coupling each of the rollers and defining a synchronous friction drive for driving each of the rollers at the same speed and equalizing the frictional forces applied to the rollers. The transmission assembly is preferably non-motorized and includes a set of drive sprockets, each of the drive sprockets being fixed for rotation on one of the rollers. The transmission arrangement also includes a set of idler sprockets, each idler sprocket being rotatably mounted on the extruder head assembly and lying in the same horizontal plane as the drive sprockets. A chain links the drive sprockets and the idler sprockets together. The chain is wound about an outer peripheral portion of the drive sprockets and an inner peripheral portion of the idler sprockets.
In yet another aspect of the invention, a concrete pipe manufacturing machine movable in a mold for receiving a concrete mixture to form a tubular concrete wall has an extruder head assembly including a troweling cylinder assembly having a head plate and a cylindrical sidewall. A vertically movable and rotatable drive shaft is fixed to the head plate for moving the troweling cylinder assembly in a vertical direction and in one rotational direction. A series of roller assemblies are rotatably mounted on the head plate and adapted to be rotated by frictional contact with the concrete wall in a direction counter to the one rotational direction of the drive shaft. Each of the roller assemblies has a stepped roller provided with a first segment and a second segment, each of the segments having different diameters. Each roller assembly further includes a shaft supporting the roller, bearing structure secured to the head plate for rotatably supporting the roller and the shaft, and a drive sprocket fixed to the shaft. A series of idler sprockets are interposed between adjacent ones of the drive sprockets. A transmitting band interengages the drive sprockets and the idler sprockets for synchronously drivingly interconnecting the rollers so as to extrude the concrete with a high degree of compaction. The stepped roller preferably has a third segment having a diameter which is different than the diameters of the first segment and the second segment. Each of the rollers extends upwardly above the head plate, and the drive sprockets, the idler sprockets, and the transmitting band are preferably disposed beneath the head plate inside the cylindrical sidewall of the troweling cylinder assembly. The bearing unit has an annular collar fixed in an upper surface of the head plate, and the collar has a height which spaces each of the rollers for rotation above the head plate.
Still yet another aspect of the invention resides in a method for manufacturing concrete pipe in a mold receiving a concrete mixture to form a tubular concrete wall with a machine having a concrete packing assembly including a troweling cylinder assembly rotatable in one direction, and a series of friction driven rollers engageable with the concrete and rotatable in a direction opposite the direction of rotation of the troweling cylinder. The method includes the steps of positioning the concrete packing assembly in a lower portion of the mold; discharging the concrete mixture into the mold to provide a supply of material on top of the concrete packing assembly; moving the concrete packing assembly longitudinally in the mold from the bottom to the top; and extruding the concrete mixture in an annular space between the concrete packing assembly and the mold by rotating the rollers in the direction opposite the direction of rotation of the troweling cylinder during the longitudinal movement of the packing assembly. Each roller preferably has a stepped configuration and the rotation of the rollers causes an increasing degree of compaction on the concrete mixture as the packing head is raised. The method further involves packing the concrete mixture by rotating the troweling cylinder during the longitudinal movement thereof, and removing the concrete wall from the mold. The step of extruding the concrete mixture includes interconnecting and collectively driving the stepped rollers together to overcome any frictional resistance tending to jam any of the rollers.